Drawing board

ABSTRACT

A small sized drawing board is provided, on which a drawing rail, preferably of triangular shape, is aligned by means of ridges or grooves at the edges. The rail is usable for the drawing of lines or alignment of other drawing devices, especially triangles, adjustable drawing heads with square rules, writing or drawing patterns, or the like.

United States Patent [1 1 Hebel et al.

[4 1 Feb. 18,1975

[ DRAWING BOARD [76] Inventors: Walter Hebel; Ulrich Hebel, both of 4 Bruckenstrasse, 5242 Kitchen 9 erman [22] Filed: Aug. 14, 1972 [21] Appl. No.: 280,270

[30] Foreign Application Priority Data Aug. 16, 1971 Germany 2140903 Feb. 7, 1972 Germany 2205621 [52] U.S. Cl 33/76 R, 33/79 R, 38/81 [51] Int. Cl B431 13/02, B43l 13/24 [58] Field of Search 33/76 R, 79 R, 81, 110

[56] References Cited UNITED STATES PATENTS 670,677 3/1901 Kelsey 33/93 795,145 7/1905 Loomis.... 1,064,222 6/1913 Holmes.... 1,975,648 10/1934 Poulsen.... 2,052,904 9/1936 Stahl 2,501,296 3/1950 Tyler 33/76 R 2,791,838 5/1957 Richter 33/110 3,508,336 4/1970 33/79 R 3,589,016 6/1971 33/76 R 3,667,126 6/1972 Wackerfuss 33/79 R FOREIGN PATENTS OR APPLICATIONS 1,810,742 2/1968 Germany 33/76 R 163,987 2/1949 Austria 33/101 743,725 11/1943 Germany 33/79 R 816,505 10/1951 Germany 33/76 R 650,598 2/1951 Great Britain 33/79 A Primary Examiner-Richard E. Aegerter Assistant Examiner-lohn W. Shepperd Attorney, Agent, or FirmNorman S. Blodgett [57] ABSTRACT A small sized drawing board is provided, on which a drawing rail, preferably of triangular shape, is aligned by means of ridges or grooves at the edges. The rail is usable for the drawing 01' lines or alignment of other drawing devices, especially triangles, adjustable drawing heads with square rules, writing or drawing patterns, or the like.

4 Claims, 12 Drawing Figures PATENIED FEB I 8 I975 sum 10F a DRAWING BOARD BACKGROUND OF THE INVENTION On small size drawing boards of this kind,'the drawing rail (also called T-square) serves on the one hand for the purpose of drawing horizontal straight lines, running parallel to each other. On the other hand, it is used for the guiding and alignment of drawing triangles, writing and drawing patterns as well as square rules with two sides arranged at a right angle to each other.

For the exact guidance and easy handling of the drawing rail, alignments between the same and the drawing board already have been created, which by means of'a guiding element embrace either aguiding ridge sitting on the drawing board or gear into a groove of the drawing board, in order to obtain thereby forcibly a parallel alignment of the drawing rail. An exact guidance of the'drawing rail, however, requires a certain minimum length of the guiding element. For this reason the drawing rails of small size drawing boards come preferably in the shape of right-angled triangles, whereby the longer cathetus (non-hypotenuse side) serves as drawing edge andfor the guiding of additional drawing devices and is provided-in the area of the short cathetus of the guidingelement.

The additional drawing devices, especially drawing triangles, squares, writing and drawing patterns or the like loosely held against the drawing edge of the drawing rail and aligned against it formlocking by hand'pressure. This method, however, is still relatively complicated, because the.additional drawing devices can lose their exact coordination to the drawing rail as soon as they are not heldtany longer by hand.

In the case of considerably larger drawing boards, it is already known that the drawing head is guided by a parallel adjustable rail with two parallel guiding edges, one of which also can be used for the drawing-of lines. A guiding skid attached to the drawing head is provided with a guidance groove and can be set upon the rail in such a manner that the sides of the groove touch the guidance edges of the rail. In this way the drawing head can be moved free of play along the rail. In order to guarantee a clean parallel shifting of the rail it is lead on both ends by tow lines. This solution cannot be applied to small size drawing boards because the drawing rail preferably is of a triangular shape and does not provide guiding edges. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

The aim of the invention is to equip a small size drawing board with an exactly aligned drawing rail by the easiest supplementary means in such a manner that one can work with it in the same way as with a drawing installation of a larger size. Thereby also for the additional drawing devices an enforced alignment at .the drawing rail is to be provided without losing the lowest possible constructional height of the drawing rail, which is necessary for its easy use and for the precision of the drawing.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION This invention involves a drafting board, a straightedge whose movement on the drafting board is restricted so that-it remains'parallel with respect to the board, and a drafting fixture whose movement is restricted to linear motion along the straight-edge. In particular, the sliding connection between the various elements of the invention is obtained by the cooperation of lands and grooves on the elements. The drafting fixture has edges which can easily be reoriented with respect to the straightedge.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood-by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a topview presentation of part of a drawing board with drawing rail aligned to it and coordinated drawing triangle,

FIG. 2 is a sectional drawing along line lllI through the drawing board as in FIG. 1,

FIG. 3 is a larger scale sectional drawing along line Ill-III of FIG. 1,

FIG. 4 is a topview presentation corresponding with FIG. 1 of a drawing rail with swingable square rule aligned thereto,

FIG. 5 is a sectional drawing along line V-V in FIG.

FIG. 6 is a larger scale sectional drawing along line VIVl in FIG. 4,

FIG. 7 is a larger scale sectional drawing corresponding with FIG. 5 through a varied application of a sliding piece forming the swivel carriage for the square rule,

FIG. 8 is a sectional drawing corresponding with FIG. 5 through again a varied application of the sliding piece serving as swivel carriage for the square rule,

FIG. 9 is a sectional drawing along line IX-IX in FIG. 8,

FIG. 10 is a sectional drawing along Line X-X in FIG. 8,

FIG. 1 l is a view in longitudinal section of a hatching device arranged at the sliding piece, and

FIG. 12 is a sectional drawing along line XII-XII in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT For the accomplishment of the task, for which the invention is conceived, it is proposed that the drawing rail provides a guidance bar and/or a guidance groove running parallel to its drawing edge, along which the additional drawing devices can be shifted by means of a sliding piece. Hereby, according to the invention, the sliding piece of the additional drawing device can be provided with a groove adapted to the guidance bar and/or a bar adapted to the guidance groove as a guiding element. It has turned out to be especially advantageous if the lateral surfaces of the bars and/or grooves are beveled wholly or in part. Preferably the bar and/or the groove of the drawing rail or the sliding piece is beveled at the bottom on one or both sides.

According to another feature of the invention the sliding piece can be fastened to the additional drawing device. Hereby it is possible to build the sliding piece as one piece with the additional drawing device, whereby it consists preferably of a groove and/or bar built immediately into a drawing triangle or a writing or drawing pattern.

However, it is especially useful if, according to the invention, the sliding piece joined to the additional drawing device is detachable. To this effect the sliding piece can be provided with coupling protrusions, e.g., two knobs, which engage and catch in corresponding coupling indentations or holes in the additional drawing device.

The use of the additional drawing device is made easier if the sliding piece is provided with a handle.

In order to solve the problem of its further use according to the invention, the sliding piece is built with a swivel carriage for a drawing head with square rule.

A design which is especially simple results, according to the invention, if the sliding piece as a swivel carriage has a circular hole, in which a salient of a corresponding diameter of the square rule catches as an abutment.

In order to effect an exact and stable adjustment of the square rule to the sliding piece serving as swivel carriage it is projected to build the hole in the swivel carriage and the corresponding salient on the square rule with a diameter as large as possible.

If according to a further feature of the invention, the hole in the sliding piece widens conically downwards, the square rule being placed underneath the sliding piece and with a conical projection on its upper side" fitting into the hole of the sliding piece, it will be possible to shift the square rule centricly in a simple but permanently precise manner.

According to another characteristic of the invention, the attachment on the square rule extends over the top of the sliding piece and can be used as a handle to swing the square rule in the swivel carriage which forms the sliding piece.

It has been proved to be especially efficient and purposeful if the conicalness of the swivel carriage lies between 2 and As far as the manufacturing is concerned, an especially simple feature of the invention consists in the fact that the square rule with its attachment and the handle is built as one piece. Furthermore hereby the square rule can have in one piece two drawing edges running at right angles to each other and consisting of transparent material.

According to the invention the square rule and/or the sliding piece forming the swivel carriage can be supplied with graduations and reading markings centrally located around the axis.

It is especially useful for the exact performance of the drawing jobs, if the base plate is provided with locking devices for the square rules. In the simplest case, these locking devices can be built on the conical surfaces of the hole in the base plate and at the attachment of the square rule. These locking devices can be put in gear by exerting pressure upon the base plate in each swivel position and also put again out of gear at any time by pressure upon the square rule.

According to the invention the locking devices, however, can also consist of a ring rotating at the base plate, above which the square rule can be locked against the base plate by means of a thread or a wedge surface. This ring can rest between the base plate and the handle and be supplied with a radial grip-wing for easier servicing.

In a further developed design, the ring will be guided centrically at its underside on a ring shoulder of the base plate and brace itself upon it also axially. On its top it has a ring groove with wedge surfaces, in which the guidance shoulder withwedge surfaces on the handle will engage. For this purpose, according to the invention, the handle engages over a central supporting attachment into a ring shoulder at the square rule and is braced against it over a screw. in a releasable manner. The square rule has on its topside'a ring-shaped bulge with a trapezoidal profile, which fits into a corresponding groove of the underside of the base plate as a locking device for the square rule. In this case, for the purpose of an exact swivel movement of the square rule, a cylindrical bearing piece is formed on and concentrically with the ring bulge, which extends into a cylindrical bearing opening of the base plate from below. The separate construction of locking device and centration for the square rule also provide for a permanently exact but easily movable positioning of the square rule at the sliding piece.

In order to make is possible to lock the square rule against the swivel carriage not only in arbitrary positions but also to fix it formlocking, the invention proposes to arrange between the base plate and the square rule an arresting device, in which the square rule can be locked in several predestined angular distances, which usually amount ot 15 each. Hereby the arresting device consists of a notch arrangement in the base plate at a central angle of at least 90 and a latch built into the handle, radially movable by a push button, which can be inserted formlocking into the notch arrangment by a spring element. In order to guarantee an exact locking of the square rule in the angular position, of 0, 15, 30, 45, 60, and at all times, also if little space is available for the locking device, the invention provides in the square rule a wedge shaped groove, and the push button is fitted correspondingly .with wedged shaped guidance surfaces for the radial movement free of play in the groove.

The notch arrangement in the sliding piece is equipped with gear profiles, running wedge-like in a radial direction, whereby the latch has corresponding notch flanks. The spring element acts radially as well as axially at the push button.

According to a further proposal for development of the invention, a hatching device is attached to the base plate of the square rule. This hatching device is in an especially useful manner easily detachable, e.g. joined to the base plate by locking means.

Naturally, it is easily possible to hold a simple drawing rule instead of the square rule angularly adjustable in the swivel carriage. If an adequate plug-in coupling installation is provided, also square rules and other rules can be exchanged with one another at random. Such a plug-in unit can e.g. be formed from the knobs located at the underside of the swivel carriage, coupled solidly with the handle, which can be locked and wedged into corresponding holes in the ruler or the square rule.

A small size drawing board 1 is equipped along its left border edge with a guiding groove 2, in which a drawing rail 3 engages by means of a guiding bar 4 so formlocking that it is aligned parallel with its drawing edge 5. Running parallel to drawing edge 5 on the drawing rail 3 a guiding bar 6 is affixed. Along this guiding bar 6 a sliding piece 7 is guided parallel movable by sliding through a groove 8 adapted to the profile.

In FIG. 1 a drawing triangle 9 is provided with holes 10 into which the knobs 11 formed on the sliding piece 7 wedge and fit in such a way that the drawing triangle 9 can be locked quickly and easily with the sliding piece 7, as can be seen from FIG. 3.

The groove 8 in sliding piece 7 is on its side which is averted from the drawing edge 5 of the drawing rail 3 provided at the bottom with a beveling 12, which through the pressure of a hand holding the slide piece 7 puts itself on the edge 13 of the guiding bar 6, thereby pulling tightly the touching edge 14 of the drawing triangle 9 to the drawing edge 5 of the drawing rail 3. Hereby a precise alignment of the drawing triangle 9 to the drawing rail 3 is accomplished.

For a comfortable handling of the drawing triangle 9 in the performance of drawing jobs the sliding piece 7 is equipped with a handle 15 on its topside.

Since the drawing triangles 9 cooperating with the drawing rail 3 frequently have to be brought in contact with various side edges on the drawing edge 5 of the drawing rail 3, it is of advantage to coordinate to each of its side edges holes 10, in which they can be locked whenever necessary with the sliding piece 7. As can be clearly seen from FIG. 4 in conjunction with the drawing rail 3 running parallel on a small size drawing board 1 (FIG. 1) instead ofa drawing triangle 9 also any other kind of a drawing or writing pattern can be used, iflike the drawing triangle 9 it is equipped with means which allow a detachable coupling with the sliding piece 7. On the other hand it is also feasible to join each additional drawing device cooperating with the drawing rail 3 securely with the sliding piece 7 effecting the parallel guidance at the drawing rail or to construct it in one piece.

Another possibility for the perfection of an additional drawing device guided parallel along the drawing rail 3 by means of a sliding piece can be seen in FIG. 4. Here as an additional drawing device a square rule 16 is being used, which preferably consists of a transparent material and has two sides, provided with two straight drawing edges 17 running at right angles to each other. The square rule 16 is built in one piece and has at its normally vertical side also an edge 18 inclining under 45 and an edge 19 inclining under 75.

This square rule 16 is coordinated to a sliding piece 20 which, according to FIGS. 5 and 6 can be shifted exactly parallel by means of a groove 21 on a guiding bar 22 of the drawing rail 3. In order to obtain the exact guidance the side surfaces 23 of the groove 21 are thereby beveled towards the base of the groove, whereby these bevelings are cooperating with the free length edges of the guiding bar 22.

The sliding piece 20 forms a swivel carriage for the square rule 16 and for this purpose is provided with a hole 24, conically widening downwards, of a relatively large diameter. With the hole 24 a correspondingly conically shaped attachment 25 at the square rule 16 cooperates, which can be so formed in one piece or fastened later to the square rule 16 in such a way that in the basic position of the square rule 16 its horizontal side lies with its border edge, which is averted from the horizontal drawing edge 17 on the drawing edge of the drawing rail 3 (FIG. 4). This edge of the horizontal square side passes over a quarter sector, concentric with the attachment 25, into the drawing edge 17 of the vertical square side. This makes it possible to swing the square rule 16 with its attachment 25 formlocking in the hole 24 of the sliding piece 20 serving as a swivel carriage.

The swinging of the square rule 16 is accomplished in a simple manner thereby the attachment 25 is extended to a handle 26, preferably grooved at its contour in form of a rotary knob, which protrudes far enough upwards from the hole 24 of the sliding piece 20. If the conicalness of the hole 24 and the coordinated attachment 25 amounts to between 2 and 10, then aside from the exact positioning also a wedging effect is reached, by which the square rule can be fastened in any desired swivel position to the sliding piece 20. Thereby a slight swinging of the square rule 16 in the sliding piece 20 in any desired position of the rule is made possible after first the wedging effect between the hole-wall 24 and the attachment 25 has been eliminated by exerting pressure on the handle 26. When the square rule, by means of its graduation in relation to the adjusting mark 28 on the sliding piece 20, has been placed in the desired swivel position, only by slight finger pressure on the sliding piece 20 the wedge effect is to be restored, to lock the square rule 16 anew in relation to the sliding piece 20. As can be seen from FIG. 4, the graduation 27 provided on the square rule 16 extends over an arc of and on the sliding piece a tongue 29 is placed, which is provided with the adjustment marking 28.

As FIG. 7 shows, the wedge effect between the conical hole 24, the sliding piece 20 and the corresponding conical attachment 25 on the square rule 16 can also be accomplished in a different manner from the one described before, and also be loosened again. According to FIG. 7 concentrically to hole 24, a turnable ring 30 is placed on the sliding piece 20, which shows at its outer contour a corrugation 31. Small bolts 32, which are driven in at least three places from outside into a concentric annular groove in the ring 30, secure the latter against axial shifting towards the sliding piece 20. On its inner side the ring 30 has a thread 33 or appropriate wedge surfaces, which are in contact with a corresponding thread 34 or adapted wedge surfaces at the service knob 26 of the square rule 16. By turning of the ring 30 in one direction the conical attachment 25 of the square rule 16 is wedged in the corresponding concial hole 24 of the sliding piece 20, while by turning of the ring 30 in the opposite direction the conical surfaces of the attachment 25 and the hole 24 are being pressed apart axially for the purpose of loosening the wedge effect. Also, in this case, the hole 24 in the sliding piece 20 and the attachment 25 on the square rule 16 have a relatively large diameter, to accomplish an exact swivel position as well as a good wedging effect.

Still another development of the swivel position of the square rule 16 in the sliding piece 20 is to be seen from FIGS. 8 to 10. Here also the sliding piece 20 is guided parallel moving lengthwise by means of a groove 21 on the guidance bar 6 of the drawing rail 3. The sliding piece 20, however, has for the swivel positioning of the square rule 16, a cylindrical hole 35 in which, from below, a cylindrical attachment 36 of the square rule 16, engages. Concentrically around the hole 35, a ring-groove 37, trapezoid-shaped in its profile, has been worked into the underside of the sliding piece 20, in which a corresponding trapezoid ringbulge 38 on the square rule 16 engages.

Concentrically with the hole 35 at the topside of the sliding piece 20, a guidance and support shoulder 39 has been constructed, exactly guiding and axially bracing a ring 40, which can be turned to a limited extent. At the top of this ring 40 we find a groove 41 with several axially ascending ring wedge surfaces 42, which cooperate with corresponding ring wedge surfaces 43 on a collar 44 of the service knob 26. Over a central support attachment 45 the service knob 26 engages solidly with the ring shoulder 46 at the square rule 16 and is detachably braced against it over a screw 47.

By turning of the ring 40 with the aid of a radial gripwing (not shown in the diagram) the square rule 16 can be shifted axially in the direction of its bearing axis towards the sliding piece 20 by means of the wedge surfaces 42 and 43 over the service knob 26. By an upward axial shifting the inclined surfaces of the trapezoid groove 37 in the sliding piece 20 and the trapezoid bulge 38 of the square rule 16 are being braced against each other and thereby effect a wedging of the square 'rule 16 against the sliding piece 20 in each swivel position of the square rule 16. By turning the ring 40 in the opposite direction over thewedge surfaces 42 and 43 and the service knob 26 an axial shifting of the square rule 16 downwards results, so that the wedge surfaces of groove 37 and bulge 38 disengage and an unimpeded swinging of the square rule 16 in the sliding piece 20 is made possible.

The bearing for the square rule 16 in the sliding piece 20, according to FIGS. 8 to 10, is also equipped with a locking device, by which the square rule 16 can be form locked closed against the sliding piece 20 in several predestined angular distances, which usually amount to each. This locking device consists of a gear tooth system with notches 48 arranged in an arc of 90 on the sliding piece 20, which show an angular distance of 15 each. In addition to this it has a latch 50, which can be shifted radially by a push-button 49 in the service knob 26 and can be inserted formlocking into the notches 48 by means of a spring element, such as a bow-shaped flatspring 51.

As FIG. 10 clearly shows, the notches 48 in the sliding piece are equipped with flanks 52 arranged wedgelike in radial direction. The part of the push-button 49 bearing the latch 50 is also tapered wedge shaped downward and sits in a corresponding wedge shaped groove in the square rule 16 (FIG. 9). Hereby the pushbutton 49 receives a formlocking radial guidance free from play in the square rule 16.

The bow shaped flatspring 51 puts the push-button 49 not only radially but also axially under tension to such an effect that the push-button 49 gets into formlocking engagement with the wedge shaped groove in the square rule 16, as does the latch 50 with the flanks 52 of the notches 48. Hereby, inspite of the small size of the locking device, an exact arrest of the square rule 16 in any lockable position free from play is guaranteed.

In FIGS. 11 and 12 a hatching device is attached to the sliding piece 20. Its case 53 is in its construction and material somewhat elastic. By pressing together the case 53 lengthwise, the barbs 54 can be locked into the slightly narrower break through opening 55 of the sliding piece 20, whereby the hatching device is held to the sliding piece and can be easily exchanged. In the case 53, an actuating lever 56 is swingable around the bearing 57. To it a step-lever 58 is adapted, which in the shape of a curve engages with a wedging effect with the guidance bar 6 of the drawing rail 3. In forcing down the actuating lever 56, the sliding piece 20 is moved by a small step to the right. The flat spring 59 lifts the actuating lever 56 with the step lever 58 each time for renewed activation back to its original position.

It shall also be mentioned that the small size drawing board 1 can be equipped along all its edges with bars for the guiding of slide rules.

On the basis of the examples of application described above ofa small size drawing board with an exactly par allel aligned drawing rail and again exactly parallel guided other drawing devices at this drawing rail, it is made clear that there is a fundamental possibility, starting with a standard equipment of simple drawing aids, like triangles, to apply in case of need, also drawing aids of a higher quality, such as drawing or writing patterns, and finally also square rule which can be adjusted to various desired degrees of angles. The latter can be equipped with so-called drawing heads of different designs, whereby the simplest construction only has a swivel and wedging carriage, which can be activated simply by finger pressure, whereas the most expensive form of construction shows beside the wedging arrest of the square rule through threads or multiple pairs of wedges also a locking device for a formlocking fixation of certain preferred squares. In each of these cases the surfaces of the swivel carriages are constructed relatively large in order to guarantee, in spite of the simplest construction, a permanently precise method of operation.

In conclusion it is to be mentioned that the swingable square rule with lockable drawing head, as it is proposed for the line up with the small size drawing board, can be outfitted instead of the spring, activating the locking device, with magnet gear to trigger the locking movements.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent l. A drafting instrument, comprising a. a drawing device,

b. a sliding piece, and

c. a connecting means between the sliding piece and the drawing device, the connecting means being adaptable to alternative selective placement in a first state wherein the sliding piece and the drawing device are movable with respect to one another, and a second state wherein the sliding piece and the drawing device are held rigid with respect to one another, the connecting means including a hole (24), a peripheral flange about the hole, a threaded, turntable ring (30) rotatably and concentrically mounted on the flange, holding means for preventing axial movement of the ring with respect to the hole, a threaded, service knob (26) engageable by the threads of the ring to draw the knob through the hole, and an abutment connected to one end of the knob to prevent the knob from passing through the hole and when the abutment is drawn adjacent the hole, to prevent rotation of the knob with respect to the hole.

2. A small size drawing board system comprising,

a. a drawing board (1),

b. a drawing rail (3) having a straight drawing edge (5) and a V-shaped groove,

a first connecting means between the board and the drawing rail to restrict the drawing rail to linear, non-rotational movement with respect to the board,

a sliding piece, which is provided with a hatching device including a case (53) mounted on the sliding piece, an actuating lever (56) swingably mounted in the case, and a step-lever (58) swingably mounted on the actuating lever and selectively engageable with the V-shaped groove to cause motion of the sliding piece longitudinally of the groove when the actuating lever is operated,

. a second connecting means between the sliding piece and the drawing rail to restrict the sliding piece to linear, non-rotational movement with respect to the drawing rail, parallel to the drawing edge,

a drawing device, and

. a third connecting means between the sliding piece 3. A small size drawing board system, comprising:

a drawing board (1),

b. a drawing rail (3) having a straight drawing edge a first connecting means between the board and the drawing rail to restrict the drawing rail to linear, non-rotational movement with respect to the board,

d. a sliding piece, e. a second connecting means between the sliding piece and the drawing rail to restrict the sliding piece to linear, non-rotational movement with respect to the drawing rail, parallel to the drawing edge,

a drawing device, and

g. a third connecting means between the sliding piece and the drawing device, the third connecting means being adaptable to selective placement in a first state in which the sliding piece and the draw ing device are movable with respect to one another, and a second state in which the sliding piece and the drawing device are held rigid with respect to one another, the third connecting means including concentric conical surface on the sliding piece I and on the drawing device, said concial surfaces being oriented for unobstructed axial movement except for surface contact with respect to one another, said surface contact resulting in a frictional engagement between the surfaces, said frictional engagement stopping axial rotation between the surfaces and resulting in the second state, the rail being provided with a groove and the sliding piece being provided with a hatching device including a case (53) mounted on the sliding piece, an actuating lever (56) swingably mounted in the case, and a step-lever (58) swingably mounted on the actuating lever and selectively engageable with the groove to cause motion of the sliding piece longitudinally of the groove when the actuating lever is operated.

4. A drafting instrument, comprising:

a. a drawing device,

b. a sliding piece, and

c. a connecting means between the sliding piece and the drawing device, the connecting means being adaptable to alternative selective placement in a first state in which the sliding piece and the drawing device are movable with respect to one another and in a second state in which the sliding piece and the drawing device are held rigidly with respect to one another, the connecting means including a wedge-shaped groove in the sliding piece, a wedgeshaped groove in the drawing device orientated approximately perpendicularly to the first groove, and a latch having wedge-shaped portions mating closely with both of said grooves, the latch, when the means is in its first state, being biased inwardly into each of the grooves and, when the means is in its second state, being disengaged from the least one of the grooves. 

1. A drafting instrument, comprising a. a drawing device, b. a sliding piece, and c. a connecting means between the sliding piece and the drawing device, the connecting means being adaptable to alternative selective placement in a first state wherein the sliding piece and the drawing device are movable with respect to one another, and a second state wherein the sliding piece and the drawing device are held rigid with respect to one another, the connecting means including a hole (24), a peripheral flange about the hole, a threaded, tuRntable ring (30) rotatably and concentrically mounted on the flange, holding means for preventing axial movement of the ring with respect to the hole, a threaded, service knob (26) engageable by the threads of the ring to draw the knob through the hole, and an abutment connected to one end of the knob to prevent the knob from passing through the hole and when the abutment is drawn adjacent the hole, to prevent rotation of the knob with respect to the hole.
 2. A small size drawing board system comprising, a. a drawing board (1), b. a drawing rail (3) having a straight drawing edge (5) and a V-shaped groove, c. a first connecting means between the board and the drawing rail to restrict the drawing rail to linear, non-rotational movement with respect to the board, d. a sliding piece, which is provided with a hatching device including a case (53) mounted on the sliding piece, an actuating lever (56) swingably mounted in the case, and a step-lever (58) swingably mounted on the actuating lever and selectively engageable with the V-shaped groove to cause motion of the sliding piece longitudinally of the groove when the actuating lever is operated, e. a second connecting means between the sliding piece and the drawing rail to restrict the sliding piece to linear, non-rotational movement with respect to the drawing rail, parallel to the drawing edge, f. a drawing device, and g. a third connecting means between the sliding piece and the drawing device, the third connecting means being adaptable to alternative, selective placement in a first state in which the sliding piece and the drawing device are movable with respect to one another, and a second state in which the sliding piece and the drawing device are held rigid with respect to one another.
 3. A small size drawing board system, comprising: a. a drawing board (1), b. a drawing rail (3) having a straight drawing edge (5), c. a first connecting means between the board and the drawing rail to restrict the drawing rail to linear, non-rotational movement with respect to the board, d. a sliding piece, e. a second connecting means between the sliding piece and the drawing rail to restrict the sliding piece to linear, non-rotational movement with respect to the drawing rail, parallel to the drawing edge, f. a drawing device, and g. a third connecting means between the sliding piece and the drawing device, the third connecting means being adaptable to selective placement in a first state in which the sliding piece and the drawing device are movable with respect to one another, and a second state in which the sliding piece and the drawing device are held rigid with respect to one another, the third connecting means including concentric conical surface on the sliding piece and on the drawing device, said concial surfaces being oriented for unobstructed axial movement except for surface contact with respect to one another, said surface contact resulting in a frictional engagement between the surfaces, said frictional engagement stopping axial rotation between the surfaces and resulting in the second state, the rail being provided with a groove and the sliding piece being provided with a hatching device including a case (53) mounted on the sliding piece, an actuating lever (56) swingably mounted in the case, and a step-lever (58) swingably mounted on the actuating lever and selectively engageable with the groove to cause motion of the sliding piece longitudinally of the groove when the actuating lever is operated.
 4. A drafting instrument, comprising: a. a drawing device, b. a sliding piece, and c. a connecting means between the sliding piece and the drawing device, the connecting means being adaptable to alternative selective placement in a first state in which the sliding piece and the drawing device are movable with respect to one another and in a second state in which the sliding piece and the drawing device are held rigidly with respect to One another, the connecting means including a wedge-shaped groove in the sliding piece, a wedge-shaped groove in the drawing device orientated approximately perpendicularly to the first groove, and a latch having wedge-shaped portions mating closely with both of said grooves, the latch, when the means is in its first state, being biased inwardly into each of the grooves and, when the means is in its second state, being disengaged from the least one of the grooves. 